Apparatus for clamping and stretching a mask

ABSTRACT

The apparatus for fabricating an organic electroluminescent device which can distribute stress applied to the mask uniformly to form precise and reliable light emitting layers is disclosed. The apparatus for fabricating an electroluminescent device according to the present invention comprises a plurality of grippers disposed in a zigzag state at a periphery of a mask for clamping the mask, a plurality of jaws formed on each gripper and contacting with the mask, and power supplying units for supplying power to the grippers to stretch the mask. Each of the grippers is divided into a connecting section connected to the power supplying unit and a head section integrated into the connecting section, and a plurality of jaws are formed on the head section of each gripper, and odd (or even)-numbered grippers disposed at each side of the mask are disposed in a more forward position than even (or odd)-numbered grippers. Accordingly, the head section of each even (or odd)-numbered gripper is placed between the connection sections of two adjacent odd (or even)-numbered grippers. The head sections of even-numbered grippers and the head sections of odd-numbered grippers are arranged alternatively in two different imaginary lines. Also, the jaws are arranged in a line on the head section of each gripper or are arranged in a zigzag state on the head section of each gripper. At this time, the jaws are arranged by equal distance from each other.

This is a divisional application of application Ser. No. 11/378,320,filed on Mar. 20, 2006, now U.S. Pat. No. 7,806,982 which claims thebenefit of Korean Patent Application No. 10-2005-0023846 filed on Mar.22, 2005, both of which are hereby incorporated by reference in theentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for fabricating anelectroluminescent display device, particularly to an apparatus forfabricating an electroluminescent display device capable of distributinga stress applied to a mask uniformly to form a precise and reliablepixel.

2. Description of the Related Art

Recently, various kinds of flat display devices having less weight andvolume have been developed to substitute the cathode ray tube (CRT)having huge weight volume. Liquid crystal display device, field emissiondisplay device, plasma display panel and electro-luminescence displaydevice (hereinafter, referred to as “EL” display device) are theexamples of such flat display devices.

Among these flat display devices, the EL display device is a self-lightemitting device in which light is emitted from fluorescent material byre-combining holes with electrons. The EL display device is classifiedinto non-organic EL display device using nor-organic material asfluorescent material and organic EL display device using organicmaterial as fluorescent material.

Compared with a passive light emitting device requiring additional lightsource such as liquid crystal display device, the EL display device isadvantageous in that the response time is short to the same level as thecathode ray tube. Also, the EL display device has many advantages suchas low-voltage drive, self-light emission, thin film shape, wide viewangle, short response time, high contrast and the like, and so isexpected to be the next generation display device.

FIG. 1 is a sectional view showing the structure of general organic ELcell for illustrating a light-emitting principle of organic EL displaydevice. The organic EL cell comprises an organic light-emitting layer110 disposed between an anode 104 and a cathode 112, the organic lightemitting layer 110 consists of an electron injection layer 10 a, anelectron transport layer 10 b, an light emitting layer 10 c, a holetransport layer 10 d and a hole injection layer 10 e.

Once power voltage is applied to the anode 104 and the cathode 112,electrons generated from the cathode 112 are transported toward thelight emitting layer 10 c through the electron injection layer 10 a andthe electron transport layer 10 b. Also, holes generated from the anode104 are transported toward the light emitting layer 10 c through thehole injection layer 10 e and the hole transport layer 10 d.Accordingly, electrons supplied through the electron transport layer 10b are collided and re-combined with holes supplied through the holetransport layer 10 d in the light emitting layer 10 c, and so and thelight is emitted. This light is radiated to an exterior through theanode 104 to display an image.

FIG. 2 is a view showing the organic EL display device.

In the organic EL display device shown in FIG. 2, first electrodes 104(hereinafter, referred to as “anodes”) and second electrodes 112(hereinafter, referred to as “cathodes”) are formed on a substrate 102in a crossing direction each other.

The anodes 104 are formed on the substrate 102 by certain distance fromeach other. On the substrate 102 on which the anodes 104 are formed, aninsulating layer (not shown) having a plurality of openings is formed,wherein each opening corresponds to an EL cell area. Walls 108 areformed on the insulating layer to divide the organic light emittinglayers 110 and the cathodes 112 formed thereon. Each wall 108 is formedin the direction perpendicular to the anodes 104, and has an inversetaper structure in which the upper end side is larger than the lower endside.

After the walls 108 are formed on the insulating layer, the organiclight emitting layers 110 made of organic material and the cathodes 112are sequentially formed on the entire insulating layer. As shown in FIG.1, the hole injection layer 10 c, the hole transport layer 10 d, thelight emitting layer 10 c, the electron transport layer 10 b and theelectron injection layer 10 a are sequentially formed to form eachorganic light emitting layer 110.

Here, red (R) colored light-emitting layer, green (G) coloredlight-emitting layer and blue (B) colored light-emitting layer areformed on the EL cell areas by using a stretched mask provided in themanufacturing apparatus.

The light emitting layer 10 c of the organic EL display device shown inFIG. 1 is formed through thermal deposition and vacuum depositionprocesses using a grill mask. The grill mask has a plurality of grillsformed thereon and corresponding to the light emitting layers to beformed on the substrate. The manufactured grill mask is stretched by amask clamping/stretching apparatus into a predetermined dimension, andthen fixed to a mask frame of the manufacturing apparatus.

In the process for forming the light emitting layer, the mask fixed tothe mask frame is placed on a surface of the substrate, and so the lightemitting layer 10 c is formed on a surface of the substratecorresponding to the grill formed on the mask.

A plurality of grippers are mounted to the mask clamping/stretchingapparatus. By pulling the grippers in the state that mask is grippedwith the grippers, the mask is stretched. In this process, a stress isapplied onto portions corresponding to each gripper in a periphery ofthe mask. If the magnitude of stress applied to one portion of the maskdiffers from that applied to another portion for some reasons, themagnitude of tension force applied to one grill differs from thatapplied to other grills depending on a position of the grill. As aresult, the stretching amounts of the grills cannot but differ from eachother.

If the stretching amounts of the grills differ from each other, sizes(areas) of the light emitting layers formed by the grills of the maskalso become different from each other. Accordingly, each light emittinglayer is not formed correctly on the predetermined position, and sizes(areas) of the light emitting layers in the display device are differentfrom each other.

SUMMARY OF THE INVENTION

The present invention intends to solve the above problem occurred in thecourse of forming the light emitting layer. Thu the object of thepresent invention is to provide an apparatus for fabricating an organicelectroluminescent device which can distribute stress applied to themask uniformly to form precise and reliable light emitting layers.

For achieving the above objects, the apparatus for fabricating anelectroluminescent device according to the present invention comprises aplurality of grippers disposed in a zigzag state at a periphery of amask for clamping the mask, a plurality of jaws formed on each gripperand contacting with the mask, and power supplying units for supplyingpower to the grippers to stretch the mask.

Each of the grippers is divided into a connecting section connected tothe power supplying unit and a head section integrated into theconnecting section, and a plurality of jaws are formed on the headsection of each gripper, and odd (or even)-numbered grippers disposed ateach side of the mask are disposed in a more forward position than even(or odd)-numbered grippers. Accordingly, the head section of each even(or odd)-numbered gripper is placed between the connection sections oftwo adjacent odd (or even)-numbered grippers.

The head sections of even-numbered grippers and the head sections ofodd-numbered grippers are arranged alternatively in two differentimaginary lines.

Also, the jaws are arranged in a line on the head section of eachgripper or are arranged in a zigzag state on the head section of eachgripper. At this time, the jaws are arranged by equal distance from eachother.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the detaileddescription in conjunction with the following drawings.

FIG. 1 is a view illustrating one pixel of a conventional organicelectroluminescent display device;

FIG. 2 is a view showing the organic electroluminescent display device;

FIG. 3 is a view showing an apparatus for fabricating an organicelectroluminescent display device according to the present invention;

FIG. 4 is an enlarged view of “A” section of FIG. 3;

FIG. 5 is a sectional view taken along a line B-B in FIG. 4;

FIG. 6 is a schematic view illustrating an even distribution of stresscaused by a plurality of the jaws on the mask shown in FIG. 4; and

FIG. 7 and FIG. 8 are views showing various arrangement states of thejaws.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the preferred embodiment of the present invention will bedescribed in detail with reference to those accompanying drawings.

FIG. 3 is a view showing a portion of the apparatus for fabricating theorganic EL display device, that is, a mask clamping/stretching apparatusaccording to the present invention.

The mask clamping/stretching apparatus 130 shown in FIG. 3 comprisesgrippers 163 disposed at long sides and short sides of a mask 160 togrip the mask; power supplying units 165 for supplying the power toenable the mask 160 to be stretched; and power transmission units 169installed for transmitting the power supplied from the power supplyingunits 165 to the grippers 163. Such mask clamping/stretching apparatus130 is supported by a clamp holder (not shown).

The mask 160 is a grill mask used for forming the R (red), G (green) andB (blue) light emitting layers 10 of the organic EL display device, andis divided into an effective area 160 a and a non-effective area 160 bexcept the effective area 160 a. A plurality of array areas P1 areformed on the effective area 160 a, and the substrate (not shown) isselectively exposed through the array areas P1 to form the lightemitting layers 160 of R (red). G (green) and B (blue) pixels. Also, aplurality of points 161 are formed on an outer periphery of theeffective area 160 a to provide a bases when the mask 160 is stretched.That is, a user decides a stretching limit on the basis of the points161 marked on the mask 160, and the mask 160 is then stretched by aforce corresponding to the stretching limit. The non-effective area 160b is a periphery area of the mask 160 except the effective area 160 a,and the grippers 163 grip the non-effective area 160 b so that a tensionforce is applied first to the non-effective area 160 b when the mask isstretched.

For example, about ten (10) grippers 163 (gripper group) are disposed ateach long side of the mask 160, and about eight (8) grippers (grippergroup) are disposed at each short side of the mask. Also, an adjustingscrew is mounted to each gripper 163 for adjusting a frictionalresistance of the gripper 163.

As shown in FIG. 3, three power supplying units 165 are disposed at eachside of the mask 160, and each of power supplying units 165 consists ofa motor 166 coupled with the power transmission unit 160 and a ballscrew box 167 coupled with the motor 166 for converting a rotationalmotion of the motor 166 into a linear motion.

Each power transmission unit 169 comprises connecting levers 171 coupledto the ball screw box 167 of the power supplying unit 165 randconnecting pins 172 coupled to the connecting levers 171. Each gripper163 is coupled with each connecting pin 172.

FIG. 4 is an enlarged view of “A” section of FIG. 3, and shows thearrangement of the grippers 163.

The grippers 163 are arranged in a zigzag state by equal distance fromeach other. On the other hand, the upper section 163 a of each gripper163 is divided into a connection section 163 a-1 coupled with thecorresponding power transmission unit 169 and a head section 163 a-2integrated into the connection section 163 a-1. As shown in FIG. 3 andFIG. 4, the width of the head section 163 a-2 is bigger than that of theconnection section 163 a-1, and the head sections 163 a-2 of all thegrippers 163 correspond to the mask 100. Here, the lower section 163 bof each gripper 163 has the same configuration as that of the uppersection 163 a.

The head sections 163 a-2 of the grippers 163 disposed at each side ofthe mask 160 are also arranged in the zigzag state. That is, forexample, odd (or even)-numbered grippers 163 are disposed in a moreforward position than the even (or odd)-numbered grippers. Accordingly,the head section 163 a-2 of each even (or odd)-numbered gripper 163 isplaced between the connection sections 163 a-1 of two adjacent odd (oreven) numbered grippers 163.

Due to such arrangement of the grippers 163, the head sections 163 a-2of the grippers 163 with a larger width are arranged alternatively intwo different imaginary lines L1 and L2, and a space between the twoadjacent grippers 163 can be remarkably reduced

FIG. 5 is a sectional view taken along line B-B in FIG. 4, and showsthat each gripper 163 consists of an upper section 163 a and a lowersection 163 b facing the upper section.

As shown in FIG. 4 and FIG. 5, three (3) or more jaws 175 each areformed on inside surfaces of the head sections of the upper section 163a and the lower section 163 b. Each jaw 175 is placed between the uppersection 163 a/the lower section 163 b and the mask 160 to transmit thepower transmitted to the gripper 163 to the mask 160.

As described above, the head sections 163 a-2 of the grippers 163 arearranged alternatively in two different imaginary lines L1 and L2, andthe width of each head section 163 a-2 is larger than that of theconnecting section 163 a-1, and so an area (that is, the area of headsection) on which the jaws 175 are disposed becomes wide.

That is, compared with the grippers having a rod shape without a headsection and the state that the sections of the grippers on which thejaws are formed are arranged in a fine, the grippers and the arrangementof the grippers as shown in FIG. 4 and FIG. 5 are advantageous in that aspace between the two adjacent grippers 163 is remarkably reduced, andmuch more jaws 175 can be formed on the head section 163 a-2 of eachgripper 163, and so a plurality of jaws 175 formed on the head sections163 a-2 of the grippers 163 are contacted densely and uniformly with themask 160 through the entire non-effective area 160 b. Consequently, itis possible to prevent the stress from being concentrated on a specificarea of the mask 160.

FIG. 6 is a schematic view illustrating even distribution of stresscaused by a plurality of jaws on the mask shown in FIG. 4. As shown inFIG. 6, the stress applied to the mask 160 is uniformly distributed onthe entire area of the mask 160 so that the mask and all the grillsformed on the mask are uniformly stretched.

FIG. 7 and FIG. 8 are views showing various arrangement states of thejaws, the jaws 175 formed on each gripper 163 can be arranged in a lineas shown in FIG. 7 and, and can be arranged in the zigzag state as shownin FIG. 8. Also, the jaws can be randomly arranged. In addition, thejaws 175 formed on each gripper 163 are arranged by equal distance fromeach other.

The mask clamping/stretching apparatus 130 having the above structure isoperated as follows.

First, after the mask 160 is loaded on a certain system, the mask isarranged at an area where the grippers 163 are placed, by a verticalmovement.

Thereinafter, the grippers 163 are moved forward to clamp the mask 160,and the motors 166 are driven. A rotational motion of each motor 166 isconverted into a linear motion through each ball screw box 167, and thentransmitted to a corresponding power transmission unit 169.

At this time, once each power transmission unit 169 to which the powerof the motors 166 is transmitted is moved backward, the grippers 163 arealso moved backward. Accordingly, the mask 160 contacting with the jaws175 of each gripper 163 is stretched outward by the grippers 163.

Then, once the mask 160 is stretched and expanded to a designed size, amask frame (not shown) is disposed below the mask 160, and then the mask160 is fixed to the mask frame by laser welding. The mask 160 fixed tothe mask frame is used in the process of forming the light emittinglayer. That is, the mask frame to which the mask 160 is fixed is placedbelow the substrate, and organic material vapor is passed selectivelythrough the grills formed on the mask 160 and reaches a predeterminedlight emitting area of the substrate. Accordingly, the organic lightemitting layer pattern corresponding to the grills of the mask 160 isformed on the substrate.

As described above, in the apparatus for fabricating an organicelectroluminescent display device according to the present invention,the grippers provided for clamping the mask are disposed in the zigzagstate, each gripper has the head section with a relatively large width,and a plurality of jaws are formed on the head section of each gripper.Thus, it is possible to prevent the stress from being concentrated on aspecific area of the mask, and distribute the stress uniformly on themask and all the grills formed on the mask.

Consequently, the light emitting layer can be formed precisely on apredetermined area of the substrate by using the mask which is uniformlystretched, thereby enhancing reliability of the organicelectroluminescent display device.

The preferred embodiments of the present invention have been describedfor illustrative purposes, and those skilled in the art will appreciatethat various modifications, additions, and substitutions are possible,without departing from the scope and spirit of the present invention asdisclosed in the accompanying claims.

1. An apparatus for clamping and stretching a mask having grills formedthereon and corresponding to light emitting areas of a substrate to formlight emitting layers of R (red), G (green) and B (Blue) pixels of theorganic electroluminescent display device, comprising, a plurality ofgrippers disposed in a zigzag state at a periphery of a mask forclamping the mask; a plurality of jaws formed on each gripper andcontacting with the mask; power supplying units for supplying power tothe grippers to stretch the mask; and power transmitting units, eachpower transmitting unit being provided between the gripper grouparranged on each side of the mask and the corresponding power supplyingunit to enable the grippers to be moved linearly, wherein each of thegrippers is divided into a connecting section connected to the powersupplying unit and a head section integrated into the connectingsection, and the plurality of jaws are formed on the head section ofeach gripper, and a width of the head section is larger than a width ofthe connecting section.
 2. The apparatus according to claim 1, whereinodd (or even)-numbered grippers disposed at each side of the mask aredisposed in a more forward position than even (or odd)-numberedgrippers.
 3. The apparatus according to claim 2, wherein the headsection of each even (or odd)-numbered gripper is placed between theconnection sections of two adjacent odd (or even)-numbered grippers. 4.The apparatus according to claim 3, wherein the head sections ofeven-numbered grippers and the head sections of odd-numbered grippersare arranged alternatively in two different lines.
 5. The apparatusaccording to claim 1, wherein the jaws are arranged in a line on thehead section of each gripper.
 6. The apparatus according to claim 1,wherein the jaws are arranged in a zigzag state on the head section ofeach gripper.